1. Field of the Invention
This invention relates to an active matrix display device, specifically to an active matrix display device in which a plurality of retaining circuits is provided.
2. Description of the Related Art
There has been a great demand on the market for portable devices with a display such as a portable TV and a portable telephone. All these devices need a small, lightweight and low power consumption display device. Development efforts have been made accordingly. A liquid crystal display device having a static memory (Static Random Access Memory; SRAM) for each of the pixel elements for displaying a still picture is disclosed in Japanese Patent Application No. 2000-282168.
The invention provides an active matrix display device including a plurality of gate signal lines disposed in one direction on a substrate and a plurality of drain signal lines disposed in a direction different from the direction of the gate signal lines. The device also has a plurality of pixel element electrodes which are selected in response to a scanning signal fed from one of the gate signal lines and are provided with an image signal fed from one of the drain signal lines. A plurality of retaining circuits are disposed corresponding to the pixel element electrodes. Each of the retaining circuits retains a voltage according to the image signal. The device also has a voltage setting device setting a voltage of the gate signal line or a voltage of the drain signal line. The display device has a normal operation mode in which an analog image is formed based on the image signal and a memory operation mode in which a digital image is formed based on the voltages retained in the retaining circuits. The voltage setting device operates in the memory operation mode.